Downlink channel transmission method and apparatus and common channel reception method and apparatus in cellular communication system supporting bandwidth scalability

ABSTRACT

Methods and apparatuses for transmitting and receiving a signal in a mobile communication system are provided. The method for receiving a signal at a User Equipment (UE) in the mobile communication system includes receiving, from a Base Station (BS), configuration information indicating whether a Broadcasting Channel (BCH) and a Synchronization Channel (SCH) are allocated in at least one subband; receiving, from the BS, a downlink control channel; and receiving, from the BS, a downlink data channel, based on the configuration information and the downlink control channel.

PRIORITY

This application is a Continuation Application of U.S. application Ser.No. 13/120,552, which was filed in the U.S. Patent and Trademark Officeon Mar. 23, 2011, and claims priority to International Appl. No.:PCT/KR2009/005298 filed Sep. 17, 2009, and to Korean Patent ApplicationNo. 10-2008-0093184 filed on Sep. 23, 2008, the content of each of whichis incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a cellular communication system and, inparticular, to methods and apparatuses for transmitting and receivingdownlink common channels such as synchronization channel and broadcastchannel in a cellular communication system supporting bandwidthscalability.

2. Description of the Related Art

Recently, Orthogonal Frequency Division Multiplexing (OFDM) is becomingvery popular for broadcast and communication systems. OFDM isadvantageous to reduce Intersymbol interference and fading caused bymultipath propagation and improve spectral efficiency with a largenumber of closely spaced orthogonal subcarriers. With these advantageousfeatures, OFDM is regarded as a promising solution for high speed datatransmission and broadband communication system and superior compared toDirect Sequence Code Division Multiple Access (DS-CDMA) technology.

FIG. 1 is a diagram illustrating an OFDM-based downlink frame structurein Evolved Universal Terrestrial Radio Access (EUTRA) specified in the3rd Generation Partnership Project (3GPP) standards. Referring to FIG.1, the 20 MHz system bandwidth 101 is divided into 100 Resource Blocks(RBs) 105. An RB consists of 12 consecutive subcarriers 103 by 14 OFDMsymbol periods. Each subcarrier 103 for one OFDM symbol duration carriesa modulation symbol of downlink channel. Each box within the resourcegrid representing a single carrier for one symbol period is referred toas a Resource Element (RE) 106. In FIG. 1, the RB is composed of total168 REs (14 OFDM symbols×12 subcarriers). A single downlink data channelcan be assigned one or more RBs for one OFDM symbol duration 104according to the data rate.

In the cellular communication system, bandwidth scalability is one ofthe key performance attributes for providing high speed wireless dataservice. For instance, the Long Term Evolution (LTE) system supportsvarious bandwidths of 20 MHz, 15 MHz, 10 MHz, 5 MHz, 3 MHz, and 1.4 MHzas shown in FIG. 2. Accordingly, the LTE service provider can select oneof the available bandwidths, and a mobile terminal also can beconfigured to support various capacities of 1.4 MHz to 20 MHz bandwidth.In order to fulfill IMT-Advanced requirements, LTE-Advanced (LTE-A)supports carrier aggregation to allocate up to 10 MHz.

In the system supporting the bandwidth scalability, the mobile terminalis required to be able to carry out the initial cell search withoutinformation on the system bandwidth. The mobile terminal can acquiresynchronization to the base station and cell ID for demodulation of dataand control information through cell search procedure. The systembandwidth information can be acquired from the Synchronization Channel(SCH) in the cell search procedure or by demodulating a BroadcastChannel (BCH) after the cell search procedure. The BCH is a channel usedfor transmitting the system information of the cell which the mobileterminal accesses and is demodulated first right after the cell searchprocedure. The mobile terminal can acquire the system information suchas the system bandwidths, System Frame Number (SFN), and physicalchannel configuration of the cell by receiving a shared control channel.

FIG. 2 is a diagram illustrating an exemplary frequency resource mappingof SCH and BCH according to a system bandwidth in a conventional systemsupporting bandwidth scalability. The mobile terminal performs cellsearch on the SCH and, once the cell search has completed successfully,acquires the system information on the cell through the BCH. In FIG. 2,the horizontal axis 200 denotes frequency in MHz, and the SCH 204 andBCH 206 having 1.08 MHz bandwidth are transmitted in the middle of thesystem bandwidth regardless of the bandwidth scale. Accordingly, themobile terminal can find the RF carrier 202 regardless of the bandwidthscale of the system and acquire an initial synchronization to the systemby performing the cell search on the SCH 204 defined by 1.08 MHzbandwidth centering on the RF carrier 202. After finding the cell, themobile terminal demodulates the BCH 206 transmitted within the same 1.08MHz bandwidth centering on the RF carrier 202 to acquire the systeminformation.

FIG. 3 is a diagram illustrating a frame format of a 10 ms radio frameof an LTE system in which the SCH and BCH are transmitted. The SCH istransmitted in the forms of Primary Synchronization Signal (PSS) andSecondary Synchronization Signal (SSS) on every 0th subframe (subframe#0) and every 5th subframe (subframe #5). Each of the PSS and SSS has alength equal to an OFDM symbol duration and transmitted through 1.08 MHzbandwidth in the middle of the system bandwidth 303 as shown in FIG. 2.The BCH 302 is transmitted for four OFDM symbol durations within thesubframe #0.

The LTE-A system supports a bandwidth wider than the LTE system forsupporting high speed data transmission and should be implemented toprovide backward compatibility for the LTE terminals to access the LTE-Asystem. For this purpose, it is required to divide the downlink band ofthe LTE-A system into subbands for the LTE terminals and transmit theSCH and BCH through all the subbands. In this case, however, the SCH andBCH are transmitted redundantly from the viewpoint of the LTE terminalhaving the capability supporting the entire system bandwidth of theLTE-A system.

SUMMARY OF THE INVENTION

In order to overcome the above problems of the prior art, the presentinvention provides methods and apparatuses for transmitting andreceiving common control channels such as the SCH and BCH in a cellularcommunication system using carrier aggregation to increase systemcapability.

Also, the present invention provides common channel transmission andreception methods and apparatuses for a cellular communication systemsupporting bandwidth scalability that are capable of reducing commonchannel overhead particularly to the mobile terminals supporting higherbandwidth capacity such as LTE-A UEs.

Also, the present invention provides common channel transmission andreception methods and apparatuses for a cellular communication systemsupporting bandwidth scalability that is capable of efficientlysignaling the common control channel information from the base stationto the mobile terminal.

According to an aspect of the present invention, a method for receivinga signal at a User Equipment (UE) in a mobile communication system isprovided. The method includes receiving, from a Base Station (BS),configuration information indicating whether a Broadcasting Channel(BCH) and a Synchronization Channel (SCH) are allocated in at least onesubband; receiving, from the BS, a downlink control channel; andreceiving, from the BS, a downlink data channel, based on theconfiguration information and the downlink control channel.

According to another aspect of the present invention, a method fortransmitting a signal at a Base Station (BS) in a mobile communicationsystem is provided. The method includes transmitting, to a UserEquipment (UE), configuration information indicating whether aBroadcasting Channel (BCH) and a Synchronization Channel (SCH) areallocated in at least one subband; transmitting, to the UE, a downlinkcontrol channel; and transmitting, to the UE, a downlink data channel,based on the configuration information and the downlink control channel.

According to another aspect of the present invention, a User Equipment(UE) of a mobile communication system is provided. The UE includes atransceiver which transmits and receives signals to and from a BaseStation (BS); and a control configured to receive configurationinformation from the BS and receive a downlink control channel from theBS and receive a downlink data channel, based on the configurationinformation and the downlink control channel, from the BS, configurationinformation indicating whether a Broadcasting Channel (BCH) and aSynchronization Channel (SCH) are allocated in at least one subband.

According to another aspect of the present invention, a Base Station(BS) of a mobile communication system is provided. The BS includes atransceiver which transmits and receives signals to and from a UserEquipment (UE); and a control unit configured to transmit configurationinformation to the UE and transmitting a downlink control channel to theUE and transmitting a downlink data channel, based on the configurationinformation and the downlink control channel, to the UE, configurationinformation indicating whether a Broadcasting Channel (BCH) and aSynchronization Channel (SCH) are allocated in at least one subband.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the presentinvention will be more apparent from the following detailed descriptionin conjunction with the accompanying drawings, in which:

FIG. 1 is a diagram illustrating an OFDM-based downlink frame structurein Evolved Universal Terrestrial Radio Access (EUTRA) specified in the3rd Generation Partnership Project (3GPP) standards;

FIG. 2 is a diagram illustrating an exemplary frequency resource mappingof SCH and BCH according to a system bandwidth in a conventional systemsupporting bandwidth scalability;

FIG. 3 is a diagram illustrating a frame format of a 10 ms radio frameof an LTE system in which the SCH and BCH are transmitted;

FIG. 4 is a diagram illustrating a structure of a system bandwidth of anLTE-A system according to the first embodiment of the present invention;

FIG. 5 is a diagram illustrating a format of SI transmitted by the LTE-Asystem according to an exemplary embodiment of the present invention;

FIG. 6 is a flowchart illustrating a camp-on procedure of the commonchannel transmission method in an LTE-A system supporting bandwidthscalability according to the first embodiment of the present invention;

FIG. 7 is a diagram illustrating a frame format of a radio frame for usein an LTE-A system according to an exemplary embodiment of the presentinvention;

FIG. 8 is a flowchart illustrating a procedure for an LTE-A UE toreceive data on the PDSCH in the LTE-A system according to an exemplaryembodiment of the present invention;

FIG. 9 is a block diagram illustrating a configuration of a base stationtransmitter for transmitting downlink physical channels in LTE-A systemaccording to the first embodiment of the present invention;

FIG. 10 is a block diagram illustrating a configuration of a LTE-A UEreceiver for receiving downlink physical channel in LTE-A systemaccording to the first embodiment of the present invention;

FIG. 11 is a diagram illustrating a structure of a system bandwidth ofan LTE-A system according to the second embodiment of the presentinvention;

FIG. 12 is a flowchart illustrating a system information transmissionprocedure of the common channel transmission method in an LTE-A systemaccording to the second embodiment of the present invention; and

FIG. 13 is a flowchart illustrating a system information receptionprocedure of the common channel transmission method in an LTE-A systemaccording to the second embodiment of the present invention.

DETAILED DESCRIPTION OF EMBODIMENTS OF THE PRESENT INVENTION

Exemplary embodiments of the present invention are described withreference to the accompanying drawings in detail. The same referencenumbers are used throughout the drawings to refer to the same or likeparts. Detailed descriptions of well-known functions and structuresincorporated herein may be omitted to avoid obscuring the subject matterof the present invention. The terms used in the following descriptionsare defined in consideration of the corresponding functions in thepresent invention and thus can be replaced with other words according tothe intention and practice of user and operator. Accordingly, thedefinitions of the terms should be made based on the contents throughthe entire description of the present invention.

While the following embodiments are directed to the common channeltransmission technique for the OFDM-based communication system,particularly abiding by the 3GPP EUTRA standard, it can be understood tothose skilled in the art that the common channel transmission techniquecan be applied to other types of communication systems having thesimilar technical background and channel format with a slit modificationwithout departing from the sprit and scope of the invention.

The main object of the present invention is to provide the methods andapparatuses for transmitting and receiving common control channels suchas SCH and BCH in the cellular communication system using carrieraggregation technique to increase system capability. Particularly in theLTE-A system aggregating multiple LTE carriers to support transmissionbandwidths of up to 100 MHz, the common control channel transmission andreception methods and apparatus of the present invention enables theLTE-A UEs communicate date with high spectral efficiency and low commonchannel overhead while maintaining backward compatibility to the LTEUEs.

The downlink physical channel transmission and reception methods andapparatuses of the present invention are described hereinafter with theexemplary embodiments.

First Embodiment

FIG. 4 is a diagram illustrating a structure of a system bandwidth of anLTE-A system according to the first embodiment of the present invention.In FIG. 4, the system bandwidth of the LTE-A system is 60 MHz, and thesystem band is composed of three 20 MHz subbands 400, 401, and 402. Eachof the subbands 400 and 401 is configured to transmit the SCH and BCH403 (or 404) in the middle of its bandwidth. Unlike the subbands 400 and401, the subband 402 is configured without transmission of the commoncontrol channels. The bandwidth configuration of FIG. 4 is depicted asan example, and the present invention can be applied when the subbandsand SCH and BCH are configured in different manner within the samesystem band.

In FIG. 4, plural UEs are depicted below the corresponding subbands 400,401, and 402 on which the UEs camp. For instance, the UE #1.1, which isan LTE UE, receives the SCH and BCH 403 in the initial cell searchprocedure and camps on the subband #0 400 so as to receive downlink datawithin the 20 MHz band of the subband #0. Similarly, the UE #1.2, whichis an LTE-A UE, camps on the subband #0 400 having 20 MHz bandwidth.Although the UE #1.1 and UE #1.2 are depicted in association with thesubband #0 400, further LTE and/or LTE-A UEs can camp on the subband #0400, and the number of UEs to camp on each subband is not restricted inthe first embodiment of the present invention. Similarly, the UE #2.1,which is an LTE UE, receives the SCH and BCH 404 in the initial cellsearch procedure and camps on the subband #1 401. The UE #4.1, which isan LTE-A UE supporting 60 MHz bandwidth, can receive data through atleast one of the subband #0 400, subband #1 401, and subband #2 402. TheUE #4.1 can perform the cell search with the SCH transmitted on thesubband #0 or subband #1 and camp on the system band to receive the datausing the entire 60 MHz bandwidth. The system band camp-on procedure ofthe LTE-A UE such as UE #4.1 is described later with reference to FIG.6.

In case of subband #2 402, neither the SCH nor the BCH is transmitted,whereby the LTE UEs cannot camp on the subband #2 to receive service.However, the LTE-A UEs such as UE #3.1 and UE #3.2 can receive theSystem Information (SI) formatted as shown in FIG. 5 and camp on thesubband #2 402 to receive service. The afore-mentioned capacity-specificcamp-on procedure is described in more detail with reference to FIGS. 5and 6.

FIG. 5 is a diagram illustrating a format of SI transmitted by the LTE-Asystem according to an exemplary embodiment of the present invention.

Referring to FIG. 5, the SI 500 includes LTE-A specific systeminformation 502 as well as the legacy LTE system information 501 carriedby the BCH. For instance, the cell configuration parameters related tothe random access channel and the physical channels such as PhysicalDownlink Control Channel (PDCCH) and Physical Downlink Shared Channel(PDSCH) can be carried by the SI 500. The individual subbands depictedin FIG. 4 can be configured such that the UEs can receive the SI 500formatted as shown in FIG. 5 on the downlink physical data channels. TheSI 500 transmitted in the LTE-A system provides the UEs with the LTE-Aspecific system information 502 in addition to the legacy LTE systeminformation 501 provided in the legacy LTE system. Accordingly, the LTEUEs receives only the legacy LTE system information 501, while the LTE-AUEs receives the LTE-A specific system information 502 as well as thelegacy LTE system information 501. For instance, the information aboutthe 60 MHz system bandwidth and three 20 MHz subbands constituting the60 MHz system band is included in the LTE-A specific system information502 such that only the LTE-A UEs can receive the LTE-A specific systeminformation 502. The LTE-A specific system information 502 can includethe information indicative of no SCH and BCH on subband #2. The SI 500can be received on the SI channel periodically transmitted within thecell or received through a dedicated Radio Resource Control (RRC) upperlayer signaling.

FIG. 6 is a flowchart illustrating a camp-on procedure of the commonchannel transmission method in an LTE-A system supporting bandwidthscalability according to the first embodiment of the present invention.In the LTE-A system according to the first embodiment of the presentinvention, the LTE UEs performs only steps 600 and 601 of FIG. 6 but notthe rest steps. That is, only the LTE-A UEs performs the entire stepsfrom 600 to 605 of the camp-on procedure predicted in FIG. 6.

Referring to FIG. 6, the LTE-A UE acquires cell ID from the SCHtransmitted on the corresponding subband and frequency and framesynchronization in the cell search procedure (600). Next the LTE-A UEacquires the information about the bandwidths of the subband acquired atstep 601, a number of transmission antennas, and configuration of randomaccess channel from the BCH and SI (601). Next, the LTE-A UE acquiresthe LTE-A specific system information through the SI 500 of FIG. 5 or adedicated RRC upper layer signaling (602). From the SI 500 or thededicated RRC upper layer signaling, the LTE-A UE can acquire theinformation about the entire system bandwidth, subbands constituting thesystem band and respective bandwidths of the subbands, presence of theSCH and BCH in each subband. Next, the LTE-A UE receives a signalingindicative of the subband on which it camps (603). Referring to theexemplary case of FIG. 4, the UE #3.1 receives a signal instructing tocamp on the subband #2 402, and the UE #4.1 receives a signalinstructing to camp on the subband #0 400, subband #1 401, and subband#2 402 simultaneously.

Once the camp-on instruction signal is received, the LTE-A UE determineswhether the subband instructed to camp on is identical with the subbandon which the SCH and BCH are received (604). If the subband instructedto camp on is identical with the subband on which the SCH and BCH, theLTE-A UE sets the reception bandwidth equal to the subband instructed tocamp on according to the system information acquired at step 601.Otherwise, if the subband instructed to camp on is different from thesub band on which the SCH and BCH are received, the LTE-A UE adjusts thecenter frequency and bandwidth of the reception frequency band to matchwith the subband instructed to camp on (605). Referring to the exemplarycase of FIG. 4, if the UE #3.1 receives the SCH on the subband #1 401 inthe cell search process at step 600, the UE #3.1 adjusts the centerfrequency and bandwidth of the reception band to be identical with thoseof the subband #2 401. In case of UE #4.1, it sets the receptionbandwidth to 60 MHz and sets the center frequency of the 60 MHzbandwidth to the center frequency of the subband #1 401.

FIG. 7 is a diagram illustrating a frame format of a radio frame for usein an LTE-A system according to an exemplary embodiment of the presentinvention. As shown in FIG. 7, the SCH, BCH, PDCCH, and PDSCH aretransmitted on the individual respective subbands.

Referring to FIG. 7, the subband #0 710 and subband #1 711 during thesubframe #0 carry the SCH 700 and 701 and BCH 702 in an OFDM systemduration for transmitting the PDSCH 704 such that the REs allocated forthose channels cannot used for transmission of the PDSCH 704. However,the subband #2 712 during the subframe #0 is dedicated to the LTE-A UEswithout resource allocation for the SCH and BCH such that the moreresources can be used for transmission of the PDSCH 704 during thesubframe #0. Accordingly, the subband #2 is superior to the subband #0710 and the subband #1 711 during the subframe #0 in view of the PDSCH704. This is an advantage obtained because the subband #2 is configuredto be dedicated to the LTE-A UEs. Although not depicted in FIG. 7,reference signals (RSs) used in downlink channel estimation fordemodulating the PDSCH are included in the PDSCH 704. Meanwhile, in thesubband #0 713 and the subband #1 714 during the subframe #5, the REsallocated for the BCH in the subband #0 710 and the subband #1 711,except for the REs for SCH 700 and 701, during the subframe #0 are usedfor the transmission of the PDSCH 704. The subband #2 715 during thesubframe #5 has no REs allocated for the SCH and BCH as during thesubframe #0 such that entire REs can be used for transmission of thePDCCH 703 and PDSCH 704.

Regardless of the subband, no SCH and BCH are transmitted during therest subframes (subframe #1 to subframe #4 and subframe #6 to subframe#9) such that entire REs of OFDM symbol durations designated for thePDSCH can be used for transmission of the PDSCH 704 as shown in thesubband #0 716, subband #1 717, and subband #2 718 during the restsubframes. Although it is depicted that the PDCCH 703 are transmitted inthe same OFDM symbol durations of all the subframes, the number of OFDMsymbols for transmitting the PDCCH can be configured differentlyaccording to the subband or subframe.

FIG. 8 is a flowchart illustrating a procedure for an LTE-A UE toreceive data on the PDSCH in the LTE-A system according to an exemplaryembodiment of the present invention.

Referring to FIG. 8, the LTE-A UE receives a PDCCH every subframe anddetermines whether any data scheduled for it exists within the subframe(800). The data scheduled for the LTE-A UE can be identified by usingthe UE ID contained in the PDCCH. Next, the LTE-A UE extracts theindices of the RBs allocated for the PDSCH from an RB index field of thePDCCH (801). Next, the LTE-A UE determines whether the SCH and BCH aretransmitted on the subband to which the RBs belongs (802). If neitherSCH nor BCH is transmitted on the subband (i.e. if the RBs belongs tothe subband which does not carry the SCH and BCH), the LTE-A UE receivesthe PDSCH without consideration of the SCH and BCH (804). That is, theLTE-A UE can receive data transmitted using the entire resources of thePDSCH in the subframe #1 to subframe #4 and subframe #6 to subframe #9since neither SCH nor BCH exists in the PDCCH of those subframes.Otherwise, if the scheduled RBs belong to the subband in which both theSCH and BCH or the SCH is transmitted, the LTE-A UE receives the datatransmitted on the resources except for the REs used for the SCH and BCHwithin the PDSCH (803). That is, the LTE-A UE receives the data on thePDSCH except for the REs used for the SCH and BCH in the subframe #0 andthe subframe #5.

FIG. 9 is a block diagram illustrating a configuration of a base stationtransmitter for transmitting downlink physical channels in LTE-A systemaccording to the first embodiment of the present invention.

Referring to FIG. 9, the base station transmitter includes a BCHsubcarrier symbol generator 903 for generating BCH subcarrier symbols, aSCH subcarrier symbol generator 904 for generating SCH subcarriersymbols, a PDCCH subcarrier symbol generator 905 for generating PDCCHsubcarrier symbols, and a PDSCH subcarrier symbol generator 906 forgenerating PDSCH subcarrier symbol. The symbols generated by the symbolgenerators are mapped by a subcarrier symbol mapper 901. That is, thesubcarrier symbol mapper 901 maps the symbols generated by the symbolgenerators 903, 904, 905, and 906 to the corresponding input ports ofthe Inverse Fast Fourier Transformer (IFFT) 900. At this time, a symbolgeneration and mapping controller 902 controls the subcarrier symbolmapper 901 to map the symbols of the corresponding subframes or subbandsto the correct input ports of the IFFT 900. Referring to the exemplarycase of FIG. 4 in which the subband #2 402 of FIG. 4 does not carry theSCH and BCH subcarrier symbol, the symbol generation and mappingcontroller 902 controls the subcarrier symbol mapper 901 such that thePDSCH symbols are mapped to the input ports of the IFFT 900 on behalf ofthe SCH and BCH symbols.

FIG. 10 is a block diagram illustrating a configuration of a LTE-A UEreceiver for receiving downlink physical channel in LTE-A systemaccording to the first embodiment of the present invention.

The LTE-A UE receiver includes an Radio Frequency/Intermediate Frequency(RF/IF) receiver 1010, an RF/IF controller 1011, a Fast FourierTransformer (FFT) 1000, a subscriber symbol demapper 1001, a PDSCHsubcarrier symbol decoder 1002, a PDCCH subcarrier symbol decoder 1003,a SCH subcarrier symbol receiver 1004, a BCH subcarrier symbol decoder1005, and a symbol decoding and demapping controller 1006.

Referring to FIG. 10, the RF/IF receiver 1011 configures the bandwidthand center frequency of the reception bandwidth for the LTE-A UE toreceive downlink signals through the subband on which the LTE-A UE campson under the control of the RF/IF controller 1011. The FFT 1000 performsFourier transformation on the downlink OFDM signals and outputs thereceived subcarrier symbols. The received subcarrier symbols are outputto the corresponding decoders by means of the symbol demapper 1001. ThePDSCH subcarrier symbol decoder 1002, PDCCH subcarrier symbol decoder1003, and BCH subcarrier symbol decoder 1005 perform decoding on thecorresponding subcarrier symbols output by the symbol demapper 101 torecover the transmitted data. The SCH subcarrier symbol receiver 1004receives the SCH symbols output by the subcarrier symbol demapper 1001and performs synchronization function base on the information containedin the SCH symbols. That is, the LTE-A UE performs correlates thereceived PSS/SSS to the available PSS/SSS sequences to find the PSS/SSSsequence of the current cell and acquire synchronization with the cellin the cell search procedure. The decoding and demapping controller 1006controls the subcarrier symbol demapper 1001 to demap the output of theFFT 1000 and output the demapped symbols to the corresponding decoders.Referring to the exemplary case of FIG. 4 in which the subband #2 402 ofFIG. 4 does not carry the SCH and BCH subcarrier symbol, the decodingand demapping controller 1006 controls the subcarrier symbol demapper1001 to demap the PDCCH from the subcarriers designated for the SCH andBCH even during the subframe #0 and subframe #5.

In FIG. 10, the RF/IF controller 1011 can be a controller, whichcontrols entire operation of the LTE-A UE, and the decoding anddemapping controller 1006 can be a signal processor for processing thesignals handled in the LTE-A UE. Also, the RF/IF controller 1011 and thedecoding and demapping controller 1006 can be integrated into a singledevice.

Second Embodiment

FIG. 11 is a diagram illustrating a structure of a system bandwidth ofan LTE-A system according to the second embodiment of the presentinvention. In FIG. 11, the system bandwidth of the LTE-A system is 60MHz, and the system band is composed of three 20 MHz subbands 1100,1101, and 1102.

Referring to FIG. 11, the system band structure of the second embodimentis identically with that of the first embodiment in number of subbandsexcept that the resource types of the respective subbands differ fromeach other. Unlike the first embodiment of FIG. 4, the subband #1 1101is designated as an anchor subband, and the rest two subbands 1100 and1102 are non-anchor subbands. In order for the LTE UEs to access thesubband #0 1100 which is non-anchor subband, the subband #0 1100 isconfigured to transmit the SCH and BCH as denoted by the referencenumber 1103 in the middle of the bandwidth. In the second embodiment ofthe present invention, also the anchor subband is configured to transmitthe SCH and BCH as denoted by the reference number 1104. Whereas, thesubband #2 1102 is configured as the LTE-A dedicated subband withouttransmission of the SCH and BCH as shown in FIG. 4. Accordingly, the UEscan perform the cell search procedure on the subband #0 1100 and subband#1 1101 at initial system access.

The key difference between the anchor subband and the non-anchor subbandis whether both the LTE-A specific system information 502 and the legacyLTE system information 501 are transmitted or only the legacy LTE systeminformation 501 is transmitted in the SI transmission process.

FIG. 12 is a flowchart illustrating a system information transmissionprocedure of the common channel transmission method in an LTE-A systemaccording to the second embodiment of the present invention. In thesystem information transmission procedure according to the secondembodiment of the present invention, the base station transmits thesystem information on the anchor and non-anchor subbands.

Referring to FIG. 12, the base station generates the legacy LTE systeminformation 501 that can be received by the LTE UEs (including LTE-AUEs) as shown in FIG. 5 (1200). Next, the base station generates theLTE-A specific system information 502 that can be received by the LTE-AUEs (excluding LTE UEs) as shown in FIG. 5, the LTE-A specific systeminformation 502 containing information on the center frequency andbandwidth of the anchor subband (1201).

Next, the base station determines whether the subband on which thesystem information (SI) 500 is transmitted is an anchor subband or anon-anchor subband (1202). If the subband is a non-anchor subband, thebase station formats the system information (SI) 500 only with thelegacy LTE system information 501 but not the LTE-A specific systeminformation 502. In this case, since the SI channel carries only thelegacy LTE system information 501, the SI overhead can be reduced in thenon-anchor subband. Otherwise, if the subband is the anchor subband, thebase station formats the system information (SI) 500 with both thelegacy LTE system information 501 and the LTE-A specific systeminformation 502 (1204). Accordingly, in order for the LTE-A UEs toacquire the mandatory system information required to access the LTE-Asystem, the LTE-A UEs must receive the SI 500 on the anchor subband.After formatting the SI 500, the base station transmits the SI 500formatted for the anchor and non-anchor subbands at a predeterminedtransmission interval.

FIG. 13 is a flowchart illustrating a system information receptionprocedure of the common channel transmission method in an LTE-A systemaccording to the second embodiment of the present invention.

Referring to FIG. 13, a UE performs a cell search procedure to acquirethe cell ID and frequency and frame synchronizations based on the SCHtransmitted on the corresponding subband (1300). Next, the UE acquiresthe system information including the bandwidth of the acquired subband,the number of transmission antennas, and the random access channelconfiguration from the BCH and SI channel (1301). Next, the UE acquiresthe frequency information including the center frequency and bandwidthof the anchor subband from the system information (1302).

Next, the UE determines whether the center frequency of the anchorsubband is identical with that of the subband on which the SCH isreceived (1303). That is, the UE determines whether the SCH is receivedon the anchor subband. If the center frequency of the anchor subband isnot identical with that of the subband on which the SCH is received, theUE changes the center frequency of the reception bandwidth to the centerfrequency of the anchor subband (104). After changing the centerfrequency of the reception bandwidth, the changed center frequencybecomes identical with the center frequency of the anchor subband,whereby the UE adjusts the reception bandwidth to be equal to thebandwidth of the anchor subband (1305) and acquires the systeminformation about the entire system bandwidth from the LTE-A specificsystem information from the SI transmitted on the anchor subband (1306).

Once the LTE-A specific system information is acquired, the UE can campon the bandwidth composed of at least one subband according to steps 603to 605 of FIG. 6.

As described above, the common channel transmission and receptionmethods and apparatuses for an LTE-A system supporting carrieraggregation according to the present invention provide at least oneLTE-A UE dedicated subband on which neither SCH nor BCH is transmitted,thereby improving downlink data transmission capacity.

Also, the common channel transmission and reception methods andapparatuses for an LTE-A system supporting carrier aggregation accordingto the present invention enables the LTE-A specific system informationto be transmitted on an anchor subband but not on other non-anchorsubbands, thereby reducing system information overhead and thusimproving downlink data throughput.

Although exemplary embodiments of the present invention have beendescribed in detail hereinabove, it should be clearly understood thatmany variations and/or modifications of the basic inventive conceptsherein taught which may appear to those skilled in the present art willstill fall within the spirit and scope of the present invention, asdefined in the appended claims.

What is claimed is:
 1. A method for receiving a signal at a terminal ina mobile communication system, the method comprising: receiving, from abase station, configuration information indicating whether abroadcasting channel (BCH) for transmitting system information and asynchronization channel (SCH) for transmitting synchronizationinformation are allocated in at least one subband; receiving, from thebase station, control information on a downlink control channel; andreceiving, from the base station, downlink data on a downlink datachannel of a subband among the at least one subband based on the controlinformation, the downlink data channel of the subband being identifiedbased on the configuration information.
 2. The method of claim 1,wherein receiving the configuration information comprises: receiving theconfiguration information on a higher layer signal.
 3. The method ofclaim 1, wherein receiving the downlink data comprises: receiving, ifthe configuration information indicates that the BCH and the SCH are notallocated in the subband among the at least one subband, the downlinkdata on a resource region for the BCH and the SCH in the subband amongthe at least one subband.
 4. The method of claim 1, further comprisingidentifying a subband for camping based on a message received from thebase station, wherein the subband among the at least one subbandincludes the identified subband for camping.
 5. A method fortransmitting a signal at a base station in a mobile communicationsystem, the method comprising: transmitting, to a terminal,configuration information indicating whether a broadcasting channel(BCH) for transmitting system information and a synchronization channel(SCH) for transmitting synchronization information are allocated in atleast one subband; transmitting, to the terminal, control information ona downlink control channel; and transmitting, to the terminal, downlinkdata on a downlink data channel of a subband among the at least onesubband; based on the control information, the downlink data channel ofthe subband being identified based on the configuration information. 6.The method of claim 5, wherein transmitting the configurationinformation comprises: transmitting the configuration information via ahigher layer signal.
 7. The method of claim 5, wherein transmitting thedownlink data channel comprises: transmitting, to the terminal, if theconfiguration information indicates that the BCH and the SCH are notallocated in the subband among the at least one subband, the downlinkdata on a resource region for the BCH and the SCH in the subband amongthe at least one subband.
 8. The method of claim 5, further comprisingtransmitting, to the terminal, a message including information on asubband for camping, wherein the subband among the at least one subbandincludes the identified subband for camping.
 9. A terminal of a mobilecommunication system, the terminal comprising: a transceiver whichtransmits and receives signals to and from a base station; and a controlunit configured to receive, from a base station, configurationinformation indicating whether a broadcasting channel (BCH) fortransmitting system information and a synchronization channel (SCH) fortransmitting synchronization information are allocated in at least onesubband, to receive, from the base station, control information on adownlink control channel, and to receive downlink data on a downlinkdata channel of a subband among the at least one subband based on thecontrol information, the downlink data channel of the subband beingidentified based on the configuration information.
 10. The terminal ofclaim 9, wherein the control unit is further configured to receive theconfiguration information via a higher layer signal.
 11. The terminal ofclaim 9, wherein the control unit is further configured to receive, ifthe configuration information indicates that the BCH and the SCH are notallocated in the subband among the at least one subband, the downlinkdata on a resource region for the BCH and the SCH in the subband amongthe at least one subband.
 12. The terminal of claim 9, wherein thecontrol unit is further configured to identify a subband for campingbased on a message received from the base station, wherein the subbandamong the at least one subband includes the identified subband forcamping.
 13. A base station of a mobile communication system, the basestation comprising: a transceiver which transmits and receives signalsto and from a terminal; and a control unit configured to transmit, to aterminal, configuration information indicating whether a broadcastingchannel (BCH) for transmitting system information and a synchronizationchannel (SCH) for transmitting synchronization information are allocatedin at least one subband, to transmit, to the terminal, controlinformation on a downlink control channel to the terminal, and totransmit, to the terminal, downlink data on a downlink data channel of asubband among the at least one subband based on the control information,the downlink data channel of the subband being identified based on basedon the configuration information and the control information.
 14. Thebase station of claim 13, wherein the control unit is further configuredto transmit the configuration information via a higher layer signal. 15.The base station of claim 13, wherein the control unit is furtherconfigured to transmit, to the terminal, if the configurationinformation indicates that the BCH and the SCH are not allocated in thesubband among the at least one subband, the downlink data on a resourceregion for the BCH and the SCH in the subband among the at least onesubband.
 16. The base station of claim 13, wherein the control unit isfurther configured to transmit, to the terminal, a message includinginformation on a subband for camping, wherein the subband among the atleast one subband includes the identified subband for camping.